Device for applying water-borne paint by means of high-speed rotary atomizers of other application systems via direct charging or contact charging

ABSTRACT

A paint storage vessel is disclosed which is subdivided by flexible insulation into two interior spaces, each connected to its own distribution line and its own paint supply line. The ring main system is connected to the two distribution lines and is effected with the interposition of an electrically insulating change-over mechanism.

The invention relates to a device for applying water-borne paint bymeans of high-speed rotary atomizers via direct charging or contactcharging, according to the preamble of the main claim.

For many reasons, so-called water-borne paint systems, which aredesirable especially for environmental reasons, are nowadays usedincreasingly for applying paints.

In contrast to a conventional undercoat or top-coat, the water-bornepaint system can, for chemically-physical reasons, not be adjusted tothe specific paint resistance normally necessary for an electrostaticprocess. It is therefore required that the normally grounded paintsupply line is electrically isolated from the spray systems which areunder a high voltage, in order to prevent, in a manner of speaking, adischarge of the high voltage. For this reason, a so-called externalcharging system, i.e. so-called external charging, has been adopted, butit was found that the efficiency of deposition was very poor, and thisbecomes particularly important, especially at high relative atmospherichumidities.

By contrast, direct charging gives better values, but the device forcarrying out such direct charging operations is expensive.

In the state of the art, it has been proposed to use two paint storagevessels for direct charging, which are both set up to be insulated fromthe ground. One paint storage vessel then supplies one or more spraysystems via a pump and a so-called booth line, while the other paintstorage vessel is designed as an intermediate filling station.

The booth ring main and the first paint storage vessel fitted with apump are here insulated from the ground and, since this paint storagevessel can take up only a limited quantity of paint material but, on theother hand, so-called continuous operation is desired, it must bereplenished when a certain paint level is reached. During normaloperation, i.e. application of the paint, the first storage vessel isfilled from the ring main with paint material and, during this period,this storage vessel is at ground potential. After the valves have beenclosed, high-voltage potential is applied to this intermediate vesselwhich is then filled. Filling of the paint storage vessel fitted with apump and interim filling of the intermediate vessel here proceed fullyautomatically.

It can be seen that, with such an arrangement, not only two paintstorage vessels must be used, but the installation cost is alsoconsiderable.

It is the object of the invention to provide a device for applyingwater-borne paints by means of high-speed rotary atomizers and so-calleddirect charging, wherein this investment in machinery, as was requiredin the state of the art, is avoided.

This object underlying the invention is achieved by the teaching of themain claim.

Advantageous embodiments are detailed in the subclaims.

SUMMARY

The invention described herein encompasses a device for applyingwater-borne paint by means of high-speed rotary atomizers and directcharging or contact charging, having a grounded ring main system forsupplying the paint to the spraying elements. A paint storage vessel isinserted between the ring main and the paint spraying element. The ringmain leads, upstream of the paint storage vessel, into a change-overmechanism which provides an insulation section between the ring main andtwo adjoining distribution lines.

The paint storage vessel is subdivided into its interior by a flexibleinsulation, the area of which corresponds to the inner periphery of onehalf of the paint storage vessel. The flexible insulation divides thepaint storage vessel into two mutually insulated parts and two resultinginterior spaces which adjoin both lines connected to the spray system.

The paint storage vessel may consist of plastic.

Expressed in other words, the invention proposes that the usuallygrounded ring main is connected, with the interposition of anelectrically insulating changeover mechanism, to two distribution lineswhich are connected to the interior of a paint storage vessel. In theinterior of this paint storage vessel, a flexible insulation is providedwhich subdivides the interior region of the paint storage vessel intotwo interior vessel spaces. The flexible insulation is here of such asize that it can adapt itself to the inner wall of the paint storagevessel in one position or in the other position. The paint storagevessel is thus subdivided, also with respect to its two vessel shellparts, by the flexible insulation into two regions which are mutuallyseparated electrically.

This is a static seal which can be electrically isolated. In contrastthereto dynamic seals cannot be electrically isolated.

The two interior spaces, thus provided, of the paint storage vessel areadjoined by two paint supply lines which are fitted at their ends withthe high-speed rotary atomizer.

The mode of operation of this arrangement is as follows:

By appropriate setting of the change-over mechanism, one of the twodistribution lines is connected to the ring main, and the interior spaceof the paint storage vessel, located in the region of the end of thisdistribution line, can then be filled with paint material, the paintsupply line connected to this interior space being closed. In this way,the entire vessel is filled via the ring main with paint material andthe flexible insulation adapts itself in the vessel to the inner wall ofthat vessel part which is not connected to the distribution lineconnected to the ring main.

When the vessel has been filled, the change-over mechanism is changedover, and paint material is then supplied from the ring main into theinterior space of that vessel which so far has not been filled withpaint material, the pressure in the ring main having the effect that theflexible insulation exerts a force on the paint present in the vessel.When the previously closed paint supply line is then opened, thepressure from the ring main via the distribution line, with theinterposition of the flexible insulation, forces the paint materialpresent in the vessel through the first paint supply line outwards tothe high-speed rotary bell, that paint supply line then being closedwhich adjoins the interior space which is connected at this time to thering main by opening of the change-over mechanism.

It can be seen that an electric isolation of potential is ensured at alltimes by the insulating section in the change-over mechanism and via theflexible insulation in the vessel, the pressure of the material in thering main being sufficient for feeding the paint to the high-speedrotary atomizers.

It is important here to note that such vessels can be made in anydesired size and that they are then a constituent of the ring main, butit is also possible that the vessels are made in a small size and canthus become a constituent of the paint supply lines or of the high-speedrotary atomizers.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in detail with reference to FIG. 1 which is across-sectional schematic diagram of an embodiment of the invention.

An illustrative example of the invention is explained below by referenceto the drawing. In the drawing, 1 marks a ring main, at the end of whicha changeover mechanism 2 is arranged. The two branches of thechange-over mechanism are connected to distribution lines 3 and 4 whichend in a paint storage vessel 5. In the illustrative example shown, thispaint storage vessel 5 is represented as a sphere or cylinder, but thisis not absolutely necessary, and the size should be adapted to theconsumption rate. Within the paint storage vessel 5, and dividing thewall of the paint storage vessel 5 into two parts mutually insulatedelectrically, a flexible insulation 6 is provided which is of such asize that it is capable of adapting itself to the inner wall of thepaint storage vessel 5. The flexible insulation 6 is here located in themiddle between the two paint storage vessel parts. Two mutuallyinsulated vessel shell parts 7 and 8 and two mutually insulated vesselinterior spaces 9 and 10 are created in this way.

Paint supply lines are connected to these interior spaces 9 and 10, apaint supply line 11 adjoining the interior space 9 and a paint supplyline 12 adjoining the interior space 10, which lines lead to the actualhigh-speed rotary atomizers-which are not shown in the drawing.

In the drawing, one position of the change-over mechanism 2 is indicatedby the arrows P, in such a way that the paint material coming from thering main 1 is fed via the distribution line 3 to the interior space 9of the paint storage vessel 5. In this state, a valve provided in thepaint supply line 11 is closed and a valve provided in the paint supplyline 12 is open. Within the paint storage vessel 5, the interior space10 formed on the other side of the flexible insulation 6 is filled withpaint material, so that the pressure of the ring main then acts via thedistribution line 3 on the outside of the flexible insulation 6, so thatthe latter is capable of forcing out the actual material present in theinterior space 10 by the paint supply line 12.

When the flexible insulation 6 has reached a position which is theconverse of that shown in the drawing, a change-over mechanism 2 ischanged over. In the meantime, the interior space 9 has been filled withpaint material, and the interior space 10 has been emptied and, bychanging over the change-over mechanism 2, a pressure is now exerted viathe distribution line 4 upon the other outside of the flexibleinsulation and, after the valve provided in the paint supply line 11 hasbeen opened, the paint material then present in the interior space 9 isforced out of the paint supply line 11, while the valve provided in thepaint supply line 12 is closed.

I claim:
 1. A device for applying water-borne paint by means ofhigh-speed rotary atomizers and direct charging or contact charging,comprising:a grounded ring main system for supplying the paint to saidhigh-speed rotary atomizers; a paint storage vessel inserted between thering main system and said high-speed rotary atomizers; a pair ofdistribution lines adjoining the paint storage vessel, and a change-overmechanism which provides an insulation section between the ring mainsystem and the two adjoining distribution lines; said ring main systemleading, upstream of the paint storage vessel, into said change-overmechanism, and said paint storage vessel being subdivided in itsinterior by a flexible insulation, the area of which corresponds to theinner periphery of one half of the paint storage vessel, the flexibleinsulation dividing the paint storage vessel into two mutually insulatedparts, and the two resulting interior spaces of the paint storage vesseladjoining booth lines connected to a spray system.
 2. A device asclaimed in claim 1 wherein the paint storage vessel consists of plastic.3. A device as claimed in claim 2 or 1 wherein the flexible insulationdivides the paint storage vessel into two vessel shell parts which aremutually insulated electrically.
 4. A device as claimed in claim 2 or 1wherein an electrically effective insulation section is provided in thechange-over mechanism.